Hexaalkyl distannanes, especially hexabutyl distannanes, are valuable and extraordinarily versatile reagents for organic synthesis. As catalysts, the hexaalkyl distannanes are attracting increasing interest in a number of different technical processes.
Detailed information can be obtained from several reviews, including: W. P. Neumann, Die Organische Chemie des Zinns, Stuttgart, Ferdinand Enke Verlag, 1967; R. C. Poller, The Chemistry of Organotin Compounds, Logos Press Ltd., 1970; M. Pereyre, J. P. Quintard, and A. Rahm, Tin in Organic Synthesis, London, Butterworth, 1987; I. Omar, Organotin Chemistry, Amsterdam, Elsevier, 1989; and P. G. Harrison, Chemistry of Tin, Glasgow, Blackie.
Various methods of preparing distannanes have been described in the prior art. However, these prior art methods are oftentimes very complicated to run, have low yields, or require such costly starting materials such as trialkyltin hydrides, which makes them unattractive for industrial applications. Thus, continued research is ongoing to develop a simple and more cost-effective method of preparing distannanes, a few of these methods are described hereinbelow.
The preparation of compounds which contain tin-to-tin bonds is described in numerous publications such as: Houben Weyl,Methoden der Organischen Chemie, Vol. 13,6 401-16; A. G. Davies and P. J. Smith, Comprehensive Organometallic Chemistry, Pergamon Press, 591; A. K. Sawyer, Organotin Compounds, Vol. 3, New York, Marcel Dekker, Inc., 1972, 823-79; and W. P. Neumann, Die Organische Chemie des Zinns, Stuttgart, Ferdinand Enke Verlag, 1967.
The condensation of trialkyltin hydrides with trialkyltin amines and alkoxides or with bis-[trialkyltin] oxides produces satisfactory yields of hexaalkyl distannanes. However, this reaction requires expensive starting materials and is difficult to handle due to the high reactivity of the starting compounds. This condensation reaction is described in W. P. Neumann & B. Schneider, Angew. Chem., Int. Ed. Engl., 3, 751 (1964) and W. P. Neumann & J. Pedain, Tetrahedron Lett., Int. (1964), 2461.
W. P. Neumann, Angew. Chem. 73, 541 (1961) discloses a method of producing high yields of hexaalkyl distannanes from trialkyltin hydrides by catalytically removing the hydrogen therefrom.
Chemical Abstract Nos. 98:89536 y and 101:111072 y describe the synthesis of distannanes from the corresponding hydrides in the presence of a palladium complex. Yields of 71 to 89% are obtained from this process. More specifically, the trialkyltin hydrides are produced in-situ by reducing the trialkyltin or triaryltin chlorides with lithium aluminum hydride.
B. Jousseaume, et al., J. Organomet. Chem , 294 (3), C41-45, discloses a process for converting bis-[trialkyltin] oxide with formic acid. However, this method produces hexaalkyl distannane which are contaminated with poly-tin compounds.
German Application No. 1 955 241 discloses a method of preparing hexaalkyl distannanes from trialkyltin formiates by thermolysis. The product obtained by this method is extensively contaminated with various decomposition side products.
Chemical Abstract No. 95:123026 g (Japanese A 56 058 981) describes a method for preparing distannanes through the complicated electrolysis of trialkyltin and triaryltin formiates.
The conversion of trialkyltin lithium or sodium with trialkyltin halides into distannanes is described by G. Wittig, et al. in Liebigs Ann. Chem., 571, 167 (1961).
U.S. Pat. No. 3,699,138 describes the preparation of distannanes from trialkyltin halides with molten sodium.
B. Jousseaume, E. Chanson, Mr. Pereyre, Organometallics, 5 (b), 1271-724 discloses a method of reducing bis-[trialkyltin]oxide with titanium, potassium, sodium, or magnesium which subsequently results in yields of about 60 to 82% of hexaalkyl distannanes.
Chemical Abstract No. 72:90593 j provides a method of converting tributyltin chloride with magnesium in tetrahydrofuran which results in yields of about 70% of hexabutyl distannanes.
Hexaalkyl distannanes can also be prepared by a Wurtz reaction from trialkyltin halides and metallic sodium in liquid ammonia or ether. This reaction is described, for example, in R. K. Ingham, S. D. Rosenberg, and H. Gilmann, Chem. Rev., 60, 459 (1960) and G. Gruttner, Chem. Ber., 1917, 50, 1808.
BE A 672 867 disclosed the conversion of sodium in tetrabutyltin with tributyltin chloride followed by a complicated process which yields 93% of hexabutyl distannane.
Despite the current state of the art, none of the references disclosed hereinabove describes the current method of preparing hexaalkyl distannanes.